Chapter 6: Microbial Nutrition and Growth

Learning Outcomes 1). List the essential nutrients of a bacterial cell 2). Differentiate between macronutrients and micronutrients 3) Construct four different terms that describe an organism's source of carbon and energy 4) Define saprobe and parasite 5). Discuss diffusiion and osmosis 6) Identify effects on a cell of isotonic, hypotonic, and hypertonic conditiones

What do bacteria require for nutritional growth?

essential + non-essential nutrients

Essential nutrient

a necessary nutrient the organism is incapable of producing on its own

Non-essential nutrient

a necessary nutrient the organism is capable of producing on its own

2 types of nutrients

• Macronutrients

• Micronutrients

Macronutrients

needed in large quantities to play a role in cell structure and metabolism

Examples of macronutrients

EX: C, H, and O

Function of hydrogen

• pH maintenance

• forming H bonds between molecules

• a source of free energy in respiration

Function of oxygen

structural and enzymatic functions of the cell

Function of nitrogen

• primary source oof this element for heterotrophs

• must first be converted into NH3

• DNA, RNA, and ATP synthesis

Function of phosphorus

• key component of nucleic acids

• important in genetics

• ATP

• phospholipids in cytoplasmic membranes

• coenzymes such as NAD+

Function of sulfur

• Essential in vitamins

• Essential in amino acids methionine and cysteine (disulfide bonds)

Micronutrients (aka trace elements)

needed in small quantities to play a role in enzyme function and maintenance

Examples of micronutrients

EX: manganese, zinc, and nickel

Potassium (K)

essential to protein synthesis and membrane function

Sodium (Na)

important for certain types of cell transport

Calcium (Ca)

stabilizer of cell wall and endospores of bacteria

Magnesium (Mg)

component of chlorophyll + a stabilizer of membranes and ribosomes

Iron (Fe)

important component of the cytochrome proteins of cell respiration

Zinc (Zn)

essential regulatory element for eukaryotic genetics

Inorganic nutrient

any compound that does not contain both carbon & hydrogen

Organic nutrient

any compound that contains both carbon & hydrogen

• a product of living things

Examples of organic nutrients

• simple molecules like methane

• large polymers like carbs, lipids, proteins, or nucleic acids

Composition of microbial cytoplasm

• 70% water

• proteins

• organic compounds (97% of cell’s dry weight)

• Elements CHONPS (96% of cell’s dry weight)

***Elements are consumed as compounds and not pure elements

Microbes categorized by their source of carbon

• Heterotrophs

• Autotrophs

Heterotroph

obtains C in organic form

Autotroph

obtains C in inorganic form (via CO2) to be converted into organic compounds to be nutritionally independent

EX: plants

Microbes categorized by their source of energy

• Phototroph

• Chemotroph

Phototroph

microbes that photosynthesize

Photoautotroph

photosynthetic. capture energy from light rays → converts it into chemical energy → produces organic CO2 from energy

Chemotroph

microbes that gain energy from chemical compounds

2 types of chemoautotrophs

• Chemoorganic autotrophs

• Lithoautotrophs

Chemoorganic autotrophs

• use organic compounds for energy

• use inorganic compounds as a carbon source

Lithoautotrophs

• rely totally on inorganic minerals

• require neither sunlight nor organic nutrients

• unique methods of getting energy

How can lithoautotrophs get energy?

can remove electrons from inorganic substrates → combine them w/ CO2 and H → creates organic molecules

Chemoheterotrophs

• Derive both carbon and energy from organic compounds

• Process these molecules through cellular

  respiration or fermentation

Heterotrophs vs Parasites vs Saprobes

All heterotrophs are parasites but some are saprobes

Saprobe

• Free-living organisms that feed and recycle organic waste/nutrients from dead organisms

• Decomposers of plant litter, animal matter, and dead microbes

Parasite

Derive nutrients from the cells or tissues of a living host ranging from viruses to helminths

Pathogen

causes damage to tissues or even death

Ectoparasites

live on the body

Endoparasites

live in the organs and tissues

Intracellular parasites

live within cells

Obligate parasites

unable to grow outside of a living host

Examples of obligate parasites

• Leprosy bacillus → causes leprosy

• Syphilis spirochete → causes syphilis

Transport mechanisms for microbes to eat

atomic/molecular movement across cytoplasmic membranes

Diffusion

gradient movement high → low concentration

Osmosis

the diffusion of water through a selectively, or differentially, permeable membrane

Osmosis of cell in hypotonic condition

water flows in → cell swells and bursts

Osmosis of cell in isotonic condition

water concentration remains the same → nothing happens

Osmosis of cell in hypertonic condition

water flows out → cell shrinks

Passive Transport

no ATP needed for high → low movement

EX: simple diffusion or facilitated diffusion

Active Transport

ATP needed for faster low → high movement via permeases/pumps

EX: Carrier-mediated active transport

Examples of substances transported actively

• monosaccharides

• amino acids

• organic acids

• phosphates

• metal ions

Endocytosis

cell encloses the substance in its membrane → forms a vacuole → engulfs the substance

Phagocytosis

amoebas and white blood cells ingest whole cells or large solid matter

Pinocytosis

Ingestion of liquids such as oils or molecules in solution (the cell is drinking lol)

Cardinal temperature for microbes

(min-optimum-max)

the maximum, minimum and optimum temperature range within which the seed of a particular species germinate

Minimum temperature

the lowest temperature that permits a microbe’s continued growth and metabolism before its cellular activities stop

Maximum temperature

the highest temperature at which growth and metabolism can proceed before proteins are denatured

Optimum temperature

an intermediate that promotes the fastest rate of growth and metabolism

Psychrophiles

• 0<15-20°C

• lower temps increase cellular activity

• Natural habitats of this type of bacteria, fungi, and algae are lakes, rivers, snowfields, polar ice, and the deep ocean

• Rarely pathogenic

Psychrotrophs

• Grow slowly in the cold

• optimum temperature between 15-30°C

Examples of psychrotrophs

Staphylococcus aureus + Listeria monocytogenes are able to grow at refrigerator temperatures and cause food-borne illness (pathogenic)

Mesophiles

• optimum 20-40°C

• Human pathogens have optimal

  temperatures between 30-40°C

• medically significant microorganisms!

• Inhabit animals and plants as well as soil and

  water in temperate, subtropical, and tropical

  regions

Thermoduric Microbes

• normally mesophiles, but higher tolerance to high temps

• contaminants of heated/pasteurized foods

Exampels of thermoduric microbes

EX: heat-resistant endospore formers such as Bacillus and Clostridium

Thermophiles

• Optimum temps <45°C to max 80°C

• Eukaryotic forms cannot survive 60°C+

• Live in soil and water associated with volcanic activity, compost piles, and in habitats directly exposed to the sun

Thermophile vs Thermoduric microbe

Thermoduric bacteria can survive at high temperatures but prefer to grow at lower temperatures

Thermophiles both survive and prefer to grow at high temperatures

Extreme thermophiles

grow between 80-121°C

Microbes in terms of range of optimum temperatures (least → greatest)

1. Psychrophile

2. Psychrotroph

3. Mesohile

4. Thermophile

5. Extreme thermophile

Atmospheric gases that influence microbial growth

O2 and CO2

• O2 has greater impact → respiratory gas + powerful oxidizing agent

Microbes categorized by oxygen use and detoxification

• Those that use oxygen and detoxify it

• Those that can neither use oxygen nor detoxify it

• Those that do not use oxygen but can detoxify it

What happens to oxygen as it enters microbial cellular reactions?

it gets transformed into several toxic products

Singlet oxygen (O)

an extremely reactive molecule → can damage and destroy a cell by the oxidation of membrane lipids

Superoxide ion (O2–)

highly reactive

Microbial defense against superoxide ions

superoxide ion → converted into H via superoxide dimutase

Hydrogen peroxide (H2O2)

toxic to cells and used as a disinfectant

Microbial defense against hyodrgen peroxide

Hydrogen peroxide → converted into H2O + O via catalase

Hydroxyl radical (OH–)

highly reactive

How do microbes defend itself against toxic byproducts?

2-step processes of converting toxic substances via enzymes

Aerobe

can use gaseous oxygen in their metabolism and possess the enzymes needed to process toxic oxygen products

Obligate Aerobe

An organism that cannot grow without oxygen

Examples of aerobes

Most fungi, protozoa, and bacteria

Bacillus species, Mycobacterium tuberculosis

Microaerophiles

are harmed by normal atmospheric concentrations of oxygen but require a small amount of it in metabolism

Examples of microaerophiles

Organisms that live in soil or water or in mammalian hosts, not directly exposed to atmosphere

Borrelia burgdorferi

Facultative anaerobes

do not require oxygen for metabolism but use it when it is present

Examples of facultative anaerobes

Many gram-negative intestinal bacteria

staphylococci

Anaerobes

lack the metabolic enzyme systems for using oxygen in respiration

Obligate anaerobe

lack the enzymes for processing toxic oxygen and die in its presence

Examples of obligate anaerobes

oral bacteria, intestinal bacteria

Aerotolerant anaerobes

do not utilize oxygen but can survive and grow to a limited extent in its presence due to alternative mechanisms to breakdown oxygen

Examples of aerotolerant anaerobes

Certain lactobacilli and streptococci, clostridial species

Capnophiles

organisms that grow best at a higher CO2 tension than is normally present in the atmosphere

Capnophilic clinical species

• Neisseria (gonorrhea, meningitis)

• Brucella (undulant fever)

• Streptococcus pneumoniae

pH tolerable by majority of organisms

6-8

Acidophiles

organisms that thrive in acidic environments

Euglena mutabilis

grows in acid pools between pH 0-1

Thermoplasma

lives in coal piles at a pH of 1-2

Picrophilus

thrives at a pH of 0.7, but can grow at a pH of 0

What acidophilic eukaryotes (fungi) affect pickled foods?

molds and yeasts because they can tolerate acidic conditions and commonly spoil them :(